P-034 - Prospective Biocontrol and Biorational Agents for Control of Apple Bitter Rot and Glomerella Leaf Spot Caused by Colletotrichum Species

Biocontrol agents are of increasing interest to apple growers seeking alternative strategies for managing Colletotrichum species that cause apple bitter rot (ABR) and Glomerella leaf spot (GLS). This fungal genus can cause crop losses ranging from 14% to 100% (ABR) and can lead to defoliation of up to 75% (GLS). With upcoming restrictions from the EPA on key multi-site fungicides such as mancozeb, ziram and ferbam, new options for their replacement are imperative. We screened 10 fungicides for their efficacy against ABR and GLS, including 3 biocontrol agents. Over two years, we assessed the efficacy of biocontrol and biorational agents compared to new synthetic materials, such as Kinoprol (FRAC 52). In 2024, Tidal Grow Spectra, Howler and Theia were effective at reducing ABR incidence by 60%, 53% and 51%, respectively, on ‘Idared’ apple trees. These biorational and biocontrol agents showed comparable performance to the synthetic materials Reason (FRAC 11), Luna Sensation (FRAC 11+7) and Kinoprol (FRAC 52), which reduced ABR incidence by 50%, 55% and 49%, respectively. These new pest management tools will provide growers with additional options to rotate in their programs for managing Colletotrichum infections.